Flat face hydraulic couplings are typically used to connect pressurized hydraulic fluid lines. Due to the construction of a connect under pressure flat face hydraulic coupling, it is not necessary to depressurize the hydraulic system.
A flat face hydraulic coupling suitable to connect under pressure typically consists of a female and a male coupling, wherein the male coupling is arranged to the pressurized fluid line. When the male coupling is inserted into female coupling, a pusher rod in the female coupling will push the first valve portion from the first to the second position. With this movement, the female coupling will seal onto the male coupling. Furthermore a small relieve passage is opened in this second position, such that the pressure over the second sealing means is relieved.
As the pressure is relieved over the second sealing means, it is possible to further insert the male coupling, wherein the second valve portion is taken along to the third position and the flow path is fully opened. In the third position, the female coupling will provide a mechanical coupling to the male coupling.
In known flat face hydraulic couplings suitable to connect under pressure, the relieve passage runs via the inner space of the valve body assembly. As a result, there will be an amount of hydraulic fluid present in the inner space of the valve body assembly. When the male connector is inserted into the female connector and the first valve portion is telescopically moved into the second valve portion, this amount of hydraulic fluid needs to be diverted, which negatively impacts the force required to connect the flat face couplings.
EP2626612A1 describes a coupling device with residual pressure relief system.
DE 202006003300 discloses a hydraulic coupling, wherein a telescopic valve body assembly is provided. The inner space is in contact with ambient air and accordingly no fluid needs to be compressed for the telescopic valve body assembly to be moved. However, in this prior art coupling, the pressure is not relieved over the second sealing means. Instead the pusher rod of the female coupling operates a small hydraulic actuator arranged in the male connector, which generates sufficient force to directly move a third valve portion and to overcome the pressure difference over the second sealing means.
The arrangement of a third valve portion and of a small hydraulic actuator results in a complex flat face male coupling suitable to connect under pressure.
Accordingly, it is an object of the invention to reduce or even remove the above mentioned disadvantages.